Process for the separation of 2-alkene-1,4-diols and 3-alkene-1,2-diols from catalysts

ABSTRACT

This invention pertains, firstly, to the use of mixtures of hydriodic acid and organic solvent soluble iodide salts as catalysts for the hydration of γ,δ-epoxyalkenes to form a mixture of the corresponding 2-alkene-1,4-diol and 3-alkene-1,2-diol isomers. Secondly, this invention describes the use of pH to control the 2-alkene-1,4-diol/3-alkene-1,2-diol product ratio, and achieve improved 2-alkene-1,4-diol selectivities by controlling the pH to near neutral values. Thirdly, this invention includes a catalyst recovery process whereby a liquid/liquid extraction is used to separate the product from the catalyst. In this extraction, γ,δ-epoxyalkene, or a γ,δ-epoxyalkene-containing organic solvent, is used to extract the catalysts from water, leaving the diol products in the aqueous phase, from which they may be subsequently recovered by distillation, extraction or by other means.

This is a provisional application Ser. No. 60/022,177 filed Jul. 17,1996.

FIELD OF THE INVENTION

This invention generally relates to a process for the preparation ofmixtures of 2-alkene-1,4-diols (hereinafter "1,4-diol") and3-alkene-1,2-diols (hereinafter "1,2-diol") from γ,δ-epoxyalkenes. Moreparticularly, the invention relates to a process for the hydrolysis ofγ,δ-epcxyalkenes to give a high 1,4-diol/1,2-diol ratio of theseisomeric products wherein a mixture of γ,δ-epoxyalkene and water iscontacted with a catalytic mixture of an iodide salt and hydriodic acidunder controlled pH conditions. The invention also relates to the use ofan γ,δ-epoxyalkene-containing organic solvent in a liquid/liquidextraction process to separate the catalyst components from the reactionproducts.

BACKGROUND OF THE INVENTION

1,4-Butanediol (BDO) is an important commodity chemical used in themanufacture of tetrahydrofuran, polyesters and polyurethanes. Most ofthe BDO produced commercially is made by the reaction of acetylene withtwo equivalents of formaldehyde followed by hydrogenation of theresulting alkyne. This process has various disadvantages including theuse of relatively expensive and hazardous raw materials.

Some BDO is also produced by the reaction of acetic acid, oxygen, and1,3-butadiene to produce 1,4-diacetoxy-2-butene which is thenhydrogenated and hydrolyzed. This process suffers from various drawbacksincluding the number of steps involved and the coproduction of3-butene-1,2-diol diacetate.

Other processes for producing BDO include the hydrogenation of maleicanhydride, and the hydroformylation of allyl alcohol followed byhydrogenation of the intermediate 4-hydroxybutyraldehyde. Theseprocesses also suffer from various drawbacks such as requiring severeoperating conditions and requiring expensive rhodium catalyst,respectively.

An attractive route to BDO is through the hydrogenation of2-butene-1,4-diol (hereinafter "1,4-butenediol"). However, there is noknown way to synthesize 1,4-butenediol safely, efficiently, andinexpensively. It is known that 3,4-epoxy-1-butene (hereinafter "EPB")can be made efficiently from 1,3-butadiene and oxygen (see, e.g., U.S.Pat. Nos. 4,897,498 and 4,950,773), but there is no known process thatcan hydrolyze EPB to 1,4-butenediol with sufficiently high yield andselectivity.

For example, in J. Am. Chem. Soc., 104, 1658-1665 (1982), Ross et al.teach that acid-catalyzed hydrolysis of EPB produces a mixturecontaining 96% 3-butene-1,2-diol (hereinafter "1,2-butenediol") and only4% 1,4-butenediol. Likewise, we have found that hydrolysis of EPB withaqueous sodium hydroxide gives 1,2-butenediol, high boilers, and littleor no 1,4-butenediol. Thus, neither acid nor base catalysis conditionsare suitable for the hydrolysis of EPB to a product containing usefullevels of the desired 1,4-butenediol isomer.

Japanese Kokai Patent No. 54-79214 describes a process that useshydriodic acid and, optionally, a transition metal compound as acatalyst for the hydrolysis of EPB to mixtures containing1,4-butenediol. Under the most selective conditions reported, the diolmixture had a 1,4/1,2 ratio of only 1.3 and a total diol yield of only59%. Thus, this process not only gives a poor yield, but is alsocorrosive. Additionally, no method for the separation of the diolproducts from the catalyst components is disclosed.

Japanese Kokai Patent No. 54-73710 describes the use of both Cu(I) andCu(II) salts as catalysts for the hydrolysis of EPB to mixtures of1,4-butenediol and 1,2-butenediol. However, the reactions shown in theexamples thereof were very slow and exhibited poor selectivity to thedesired 1,4-isomer. For example, after 50 hours at elevated temperature,CuBr provided a mixture of diols having a 1,4/1,2 isomer ratio of only0.34. Moreover, there is no disclosure of a process for separating andrecovering the catalyst from the reaction product mixture.

U.S. Pat. No. 5,530,167 discloses a process for the hydrolysis of EPB toform a mixture of diols using a supported-copper catalyst. In an examplethereof, it is reported that a NaY zeolite supported copper(II) catalystgave a 1,4/1,2 ratio of 0.93.

Japanese Kokai Patent No. 57-2227 discloses a process for the hydrolysisof EPB to diols in the presence of an alkali metal iodide,alkaline-earth metal iodide, or zinc iodide and an acid selected fromsulfuric acid, hydrochloric acid, hydrobromic acid, hydriodic acid,phosphoric acid and sulfonic acid. Under the best conditions reported,the 1,4/1,2 ratio was 5.15. Again, this process is highly corrosive andno method is disclosed for the separation of the products from thecatalyst components.

Other known processes for the preparation of mixtures of 1,4-butenedioland 1,2-butenediol from EPB provide very low 1,4/1,2 ratios. Forexample, it is disclosed in DE 4429700 that EPB is hydrolyzed in thepresence of rhenium oxide to give 3% 1,4-butenediol and 65%1,2-butenediol (1,4/1,2 ratio=0.05). DE 4429699 discloses the hydrolysisof EPB in the presence of an insoluble oxide catalyst (e.g., 59% SiO₂,38% TiO₂ and 0.25% F) to give 7% 1,4-butenediol and 54% 1,2-butenediol(1,4/1,2 ratio=0.13). And DE 4342030 discloses that non-catalyzedhydrolysis of EPB at 100° C. gave 100% conversion to a productcontaining 14% 1,4-butenediol and 71% 1,2-butenediol (1,4/1,2ratio=0.20).

From the above, it can be seen that non-iodide processes for thehydrolysis of EPS give very low 1,4/1,2 ratios. While known iodideprocesses provide relatively higher 1,4/1,2 ratios, the ratio is stillnot high enough and its variability is not low enough for thehydrogenation of 1,4-butenediol to be an attactrive route to BDO.Moreover, such iodide processes are highly corrosive and, therefore, arenot very attractive. Further, in the iodide processes, there is nodisclosure of a method for separating the resulting products from thecatalyst components. Thus, a need exists in the art for a process thatcan efficiently and selectively hydrolyze EPB to a product abundant in1,4-butenediol with less corrosive effect. There is also a need in theart for a process for separating the resulting diol products from thecatalyst components.

Accordingly, it is an object of the present invention to provide aprocess for the preparation of mixtures of 1,4-diol and 1,2-diol fromγ,δ-epoxyalkenes such as EPB having improved 1,4/1,2 selectivity andreduced variability.

It is a further object of the present invention to provide a process forthe separation of catalyst components from the 1,4-diol and 1,2-diolproduct mixture.

These and other objects of the present invention will become apparent inlight of the following specification, and the appended drawings andclaims.

SUMMARY OF THE INVENTION

In a first aspect, the present invention relates to a process for thepreparation of mixtures of 2-alkene-1,4-diols (hereinafter "1,4-diol")and 3-alkene-1,2-dials (hereinafter "1,2-diol") by reacting anγ,δ-epoxyalkene with water in the presence of an organic solvent solubleiodide salt and at least one of hydriodic acid, iodoalcohol, andprecursors thereof.

In a second aspect, the present invention relates to a process for thepreparation of mixtures of 1,4-diol and 1,2-diol from γ,δ-epoxyalkeneswherein the pH is controlled to obtained a desired selectivity of1,4-diol/1,2-diol. The process includes the steps of:

(a) combining (i) an iodide salt with (ii) at least one of hydriodicacid, iodoalcohol, and precursors thereof and (iii) water to form anaqueous reaction mixture; and

(b) adding γ,δ-epoxyalkene to the aqueous reaction mixture at a rateeffective to maintain a substantially constant pH.

Preferably, the pH is maintained between about 5 and about 9 to maximizethe selectivity of the 1,4-diol isomer. In an alternative embodiment,the pH is maintained at greater than about 9 or less than about 5 toincrease the selectivity of the 1,2-diol isomer.

In a third aspect, the present invention relates to a process for theseparation of mixtures of 1,4-diol and 1,2-diol from an aqueous mixturecomprising (A) an iodide salt, (B) at least one of hydriodic acid,iodoalcohol, and precursors thereof, and (C) 1,4-diol and 1,2-diol. Theprocess includes the step of contacting the aqueous mixture with anγ,δ-epoxyalkene-containing organic extraction solvent at conditionseffective to convert the hydriodic acid, if present, to iodoalcohol andto form an aqueous phase comprising the 1,4-diol and 1,2-diol, and anorganic phase comprising the iodoalcohol and iodide salt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of pH and weight of EPB versus time for the reactionof EPB with HI, MeBu₃ NI, and water where the EPB is added all at once.

FIG. 2 is a graph of pH and weight of EPB versus time for the reactionof EPB with HI, MeBu₃ NI, and water where the EPB is added at a ratesuch that the pH is maintained substantially constant.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS

The first aspect of the present invention relates to a process for thepreparation of mixtures of 1,4-diol and 1,2-diol by reacting anγ,δ-epoxyalkene with water in the presence of an organic solvent solubleiodide salt and at least one of hydriodic acid, iodoalcohol, andprecursors thereof.

Various γ,δ-epoxyalkenes are suitable for the preparation of mixtures of1,4-diol and 1,2-diol in the process of the present invention. Examplesof such γ,δ-epoxyalkenes include, but are not limited to3-methyl-3,4-epoxy-1-butene, 2-methyl-3,4-epoxy-1-butene,2,3-dimethyl-3,4-epoxy-1-butene, 3,4-epoxy-1-butene, and the like. Thepreferred γ,δ-epoxyalkene is 3,4-epoxy-1-butene which produces a mixtureof 2-butene-1,4-diol (hereinafter "1,4-butenediol") and3-butene-1,2-diol (hereinafter "1,2-butenediol").

Sufficient amounts of water should be present to facilitate thehydrolysis of the γ,δ-epoxyalkene to obtain a mixture of thecorresponding 1,4-diol and 1,2-diol. Preferably, from 2 to 100 parts byweight of water is used per 1 part by weight of the γ,δ-epoxyalkene.

By "organic solvent soluble iodide salt", we mean an iodide salt that issufficiently soluble in an organic extraction solvent such that theiodide salt may be extracted from an aqueous phase containing the sameinto an organic phase containing the organic extraction solvent.Examples of such iodide salts and the organic extraction solvent aremore fully discussed below in the second and third aspects of theinvention.

By "iodoalcohol", we mean an isomeric adduct or a mixture of isomericadducts formed from the reaction of hydriodic acid (HI) and theγ,δ-epoxyalkene. And by "precursors thereof", we mean a compound that iscapable of reacting to form HI and/or iodoalcohol under reactionconditions without adversely affecting the desired chemistry. Suchcompounds are more fully discussed below in the second aspect of theinvention.

Sufficient amounts of the catalyst components should be used in order toobtain a desired rate of reaction. The preferred amounts of the catalystcomponents are also more fully discussed below in the second aspect ofthe invention.

Preferably, the reaction is carried out at a temperature between 50° and100° C., and a pressure of 1 to 10 bars.

For ease in understanding the remaining aspects of the invention, theywill be described hereinafter with particular reference to the preferredstarting compound of 3,4-epoxy-1-butene (hereinafter "EPB"). However,other γ,δ-epoxyalkenes can be used in the present invention to makemixtures of the corresponding 1,4-diol and 1,2-diol. Exemplaryγ,δ-epoxyalkenes suitable for use in the present invention include, butare not limited to 3-methyl-3,4-epoxy-1-butene,2-methyl-3,4-epoxy-1-butene, 2,3-dimethyl-3,4-epoxy-1-butene, and thelike.

The second aspect of the invention is based, in part, on the surprisingdiscovery that the pH of aqueous solutions of HI and an iodide salt isstrongly dependent on the EPB concentration. That is, HI/iodide saltsolutions which are initially strongly acidic (pH of about 1-2) canbecome strongly basic (pH of about 9-10 or higher) at sufficiently highEPB concentrations. For example, addition of 6.96 g of EPB to a mixtureof 0.85 grams of 57% aqueous hydriodic acid, 66.48 grams of water, and32.86 grams of methyltributylammonium iodide (MeBu₃ NI) at 64° C. causesthe pH to rise from 1.05 to 9.06. As the EPB is consumed, the pH falls,slowly at first, but then eventually dropping sharply, giving a pHversus time curve similar to that of an acid-base titration. See, e.g.,FIG. 1. FIG. 1 will be discussed more fully below in Example 4.

Without wishing to be bound by theory, we attribute this result to theeffects of reversible attack by iodide ion on EPE to generate a mixtureof iodobutenols (4-iodo-2-buten-1-ol, 2-iodo-3-buten-1-ol, and/or1-iodo-3-buten-2-ol) and hydroxide ion in aqueous solution. Thisreaction is shown in equation 1 below. ##STR1##

As the EPB concentration is increased, the equilibrium shifts to theright to generate more hydroxide and raise the pH. In the presence ofdissolved iodide, the allylic iodobutenols are in equilibrium. This isshown in equation 2 below. ##STR2##

Reaction of the iodobutenols with water forms the butenediol products,liberates HI, and lowers the pH. This reaction is shown in equation 3below. ##STR3##

Depending on the pH, the reaction of the iodobutenols with hydroxideanion may also be important. In which case, iodide anion is theco-product, and the pH falls as hydroxide anion is consumed. In eithercase, if the concentration of EPB is controlled, the pH can bemaintained at a substantially constant level. Alternatively, pH controlmay be achieved or assisted by the use of buffers as are familiar tothose skilled in the art. Any buffer may be used in the presentinvention so long as it is substantially non-reactive with theγ,δ-epoxyalkene, products, and catalyst components.

By maintaining the pH at a desired level, the formation of either1,4-butenediol or 1,2-butenediol can be maximized or increased. Forinstance, if the formation of 1,4-butenediol is to be maximized, thenthe pH should be maintained at a near neutral value, which minimizes1,2-butenediol formation via acid or base catalyzed hydrolysismechanisms. On the other hand, if the formation of 1,2-butenediol is tobe increased, then the pH should be maintained at strong acidic or basicconditions.

Accordingly, in a particularly preferred embodiment, the process for thepreparation of mixtures of 1,4-butenediol and 1,2-butenediol accordingto the second aspect of the present invention comprises the steps of:

(a) combining (i) an iodide salt with (ii) at least one of hydriodicacid, iodobutenol, and precursors thereof and (iii) water to form anaqueous reaction mixture; and

(b) adding 3,4-epoxy-1-butene to the aqueous reaction mixture at a rateeffective to maintain a substantially constant pH. By "substantiallyconstant pH", we mean that the pH is maintained within the range whichmaximizes the production of either 1,4-butenediol or 1,2-butenediol.

When the yield of 1,4-butenediol is to be maximized, the reactiontemperatures and pH should be such that the direct reaction of waterwith EPB is minimized relative to the iodobutenol-mediated reaction. Inthis case, temperatures of 50°-100° C. are preferred, with temperaturesbetween 60° and 80° C. being most preferred, while pHs between about 5and about 9 are preferred, with pHs between about 7 and about 8.5 beingmost preferred.

When more 1,2-butenediol is desired, the reaction conditions may beadjusted to increase the relative amount of 1,2-butenediol by loweringthe catalyst concentration and/or raising the reaction temperatureand/or adjusting the EPB concentration or added HI to give a higher orlower pH, e.g., greater than about 9 or less than about 5.

This process is preferably carried out at atmospheric pressure. However,it should be noted that the process can be operated at reduced orelevated pressure.

Without considering catalyst recovery, any iodide salt that is solublein the aqueous reaction mixture at reaction conditions and that has acounter-ion that does not interfere with the desired chemistry can beused in the present invention. Examples of suitable iodide salts includecompounds of the type R¹ R² R³ R⁴ E⁺ I⁻, wherein R¹, R², R³ and R⁴ aregroups containing only carbon and hydrogen, and E is nitrogen,phosphorous or arsenic, with tetraalkylammonium iodides being preferred.Metal iodides including, but not limited to alkali metal iodides andalkaline earth metal iodides, and crown ether complexes or podandcomplexes thereof may also be used. N-alkylpyridinium iodides,phosphazenium iodides, phosphazanium iodides, and cobaltacenium iodidesare also included. HI salts of sterically hindered pyridines, includingpolymeric compounds, may also be used and may serve as a source ofeither the soluble iodide or HI or both. Examples of such stericallyhindered pyridines include 2,6-dimethylpyridine,2,4,6-trimethylpyridine, 2,6-di-tert-butylpyridine,2,6-di-tert-butyl-4-methylpyridine, 2,4,6-tri-tert-butylpyridine,2,6-diphenylpyridine, 2,4,6-triphenylpyridine, acridine, and1,2,3,4,5,6,7,8-octahydroacridine. Of course, the sterically hinderedpyridine used should be substantially non-reactive with theγ,δ-epoxyalkene, products, and catalyst components.

Enough iodide salt should be present to give an adequate reaction rate;iodide salt concentrations of about 0.25 to about 1N are preferred. Ifthe catalyst is to be recovered by liquid-liquid extraction using EPB oran EPB-containing organic solvent, then the iodide salt should also havean extraction selectivity for the organic phase of greater than 1.

Either HI, iodobutenol, or precursors thereof or mixtures of thosecomponents can be used in combination with the iodide salt. By"iodobutenol", we mean an isomeric adduct or a mixture of isomericadducts formed from the reaction of HI and EPB which includes1-iodo-3-buten-2-ol, 2-iodo-3-buten-1-ol, and 4-iodo-2-buten-1-ol. By"precursors thereof", we mean a compound that is capable of reacting toform HI and/or iodobutenol under reaction conditions without adverselyaffecting the desired chemistry. Suitable precursors capable of reactingto form HI and/or iodobutenol include, but are not limited to iodine,organic iodides capable of liberating iodine, potassium triiodide andother triiodide salts, tertiary-butyl iodide, allyl iodide and otherorganic iodides subject to elimination or hydrolysis to liberate HI,collidinium hydroiodide and other adducts of HI with bases that areotherwise unreactive under the conditions of the process, zinc iodide,titanium tetraiodide and other metal iodides which can be hydrolyzed torelease HI, mixtures of a strong acid (e.g., HCl, HBr, H₂ SO₄, H₃ PO₄and other acids whose conjugate bases are otherwise unreactive under theconditions of the process) and an iodide salt, mixtures of iodide saltsand any compound subject to hydrolysis to generate a strong acid.

Enough HI, iodobutenol, or precursor thereof should be used to give anadequate reaction rate. Initial concentrations of HI, iodobutenol, orprecursor thereof between about 0.01 and about 0.25N are preferred.

It may be beneficial under certain circumstances to use a cosolvent inthe present invention. The purpose of such optional cosolvents includesolubilization of catalysts, γ,δ-epoxyalkene, and/or products in thereaction mixture. The cosolvent used should be substantiallynon-reactive with the γ,δ-epoxyalkene, products, and catalystcomponents. Examples of suitable cosolvents include acetone,acetonitrile, dioxane, tetrahydrofuran, 1-methyl-2-pyrrolidinone,N,N-dimethylformamide, and 2,5-dihydrofuran (hereinafter "DHF"). Ifsubstantial amounts of a cosolvent and/or solutes are used, then thepreferred pH ranges mentioned herein may vary.

Experiments in which the pH is controlled in the 6-8 range give1,4-diol/1,2-diol ratios in the range of about 5:1 to about 12:1. Thisrange of selectivity represents a substantial improvement over previous,non-pH controlled approaches. Moreover, the near neutral pH conditionsresult in reaction mixtures which are less corrosive than the highlyacidic mixtures of the prior art.

The conversion of HI to iodobutenol by reaction with EPB also forms thebasis for a catalyst recovery scheme. If the aqueous product-containingfeed is intimately contacted with pure EPB, or with an EPB-containingorganic phase, then virtually all of the HI is converted intoiodobutenol and extracted into the organic phase. If the iodide saltco-catalyst used has an extraction selectivity into the organic phase ofgreater than 1, then both the HI and the iodide salt catalysts can beefficiently separated from the highly water-soluble butenediol productsvia liquid-liquid extraction.

Accordingly, in a particularly preferred embodiment, the third aspect ofthe present invention relates to a process for separating mixtures of1,4-butenediol and 1,2-butenediol from an aqueous mixture comprising (A)an iodide salt, (B) at least one of hydriodic acid, iodobutenol, andprecursors thereof, and (C) 1,4-butenediol and 1,2-butenediol. Theprocess includes the step of contacting the aqueous mixture with anEPB-containing organic extraction solvent at conditions effective toconvert the HI, if present, to iodobutenol and to form an aqueous phasecomprising the 1,4-butenediol and 1,2-butenediol, and an organic phasecomprising the iodobutenol and iodide salt.

EPB may be used alone for extraction or in combination with aco-extraction solvent. At least some EPB is needed during extraction toensure complete conversion of HI to the easily extractable iodobutenolsand to avoid production of HI. Thus, the preferred extraction solvent iseither EPB or a mixture of solvents that includes EPB.

The co-extraction solvent employed may be selected from a variety oforganic solvents, depending on the chosen catalysts. Generally, theco-extraction solvent should satisfy four criteria: (1) it should form aseparate liquid phase at equilibrium when contacted with the aqueousproduct-containing feed; (2) it should have a higher extractionselectivity for the iodobutenol and iodide salt catalysts than thebutenediol products; (3) it should have characteristics that enable itto be recycled directly to the reactor and/or separated from thecatalyst components by evaporation, distillation, crystallization,decantation, or some other separation operation; and (4) it should besubstantially non-reactive with the EPB, products, and catalystcomponents.

Exemplary suitable co-extraction solvents include hydrocarbons(aliphatic and aromatic), haloaromatics, ketones, esters, ethers,amides, and mixtures thereof. Examples of hydrocarbon co-extractionsolvents include: straight- and branched-chain alkanes containing fromabout 5 to 20 carbon atoms; aromatics such as benzene, toluene, andxylene; and straight- and branched-chain alkenes containing from about 5to 20 carbon atoms. Examples of haloaromatics include: chlorobenzene,dichlorobenzene, and difluorobenzene. Examples of esters include: ethylacetate, isopropyl acetate, n-propyl acetate, isobutyl acetate, andn-butyl acetate. Examples of ketones include: methyl ethyl ketone,methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone,diisobutyl ketone, and cyclohexanone. Examples of ethers include:diethyl ether, methyl t-butyl ether, and 2,5-dihydrofuran. Examples ofamides include: 1-cyclohexyl-2-pyrrolidinone.

Alternatively, it is possible to use a dense gas as a co-extractionsolvent for the catalyst species. Exemplary dense gases include, but arenot limited to carbon dioxide, methane, ethane, propane, butane,isobutane, dimethyl ether, fluorocarbons, and mixtures thereof. Thedense gas may contain one or more cosolvents to improve extractabilityof the iodide salts and iodoalcohols. Such cosolvents include, but arenot limited to acetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, andmixtures thereof.

In this aspect of the invention, the iodide salt co-catalyst should havesolubility properties such that it can both dissolve in the aqueousreaction mixture and be later recovered in the organic phase used forthe catalyst recovery. The iodide salt co-catalyst and the iodoalcoholshould be selectively extracted into the organic phase with respect tothe 1,2- and 1,4-diols. Thus, the quaternary ammonium, phosphonium, andarsonium iodides are preferred. Tetraalkylammonium iodides are mostpreferred for this purpose, with MeBu₃ NI being especially preferred.

In the case where the catalyst employed to prepare mixtures of 1,4-dioland 1,2-diol is an HI salt of a sterically hindered pyridine, the HIsalt can be extracted from the aqueous product mixture without the useof a γ,δ-epoxyalkene-containing extraction solvent. Such salts cansimply be extracted with any of the aforementioned co-extractionsolvents.

The separation process of this invention may be carried out in batch,semi-continuous, or continuous modes of operation. For example, batchoperation may comprise charging the aqueous product-containing feed andthe extraction solvent to a vessel, agitating the dispersion to effectmass transfer, and separating the two immiscible liquid phases. One ofthe resulting liquid phases comprise the extraction solvent containingthe iodobutenol and iodide salt. We prefer the use of EPB as theextraction solvent since it can be recycled directly to the reactorwithout the need for separating the catalysts from the extractionsolvent. The second liquid phase, which is aqueous and contains thebutenediols, may be extracted repeatedly, as needed, to give the desireddegree of catalyst recovery before the stream is treated to recover thebutenediol products. These repeated extraction steps include contactingthe aqueous phase with the extraction solvent in a crossflow,co-current, or countercurrent pattern.

The extraction process is preferably operated continuously orsemi-continuously in a countercurrent manner. This technique, as wellknown in the art, can give excellent efficiencies of extraction. See,for example, T. C. Lo, M. H. I. Baird, C. Hanson, Handbook of SolventExtraction, Reprint Edition, Krieger Publishing Company, Malabar, Fla.,1991. Typical countercurrent extraction equipment generally includescolumns (agitated and non-agitated), mixer-settlers, and centrifugalextractors. Examples of agitated columns include: the Karr reciprocatingplate, rotating disc, asymmetric disc, Kuhni, York-Scheibel, and theOldshue-Rushton. Examples of non-agitated columns include: spray, baffleplate, packed, and perforated plate. Examples of centrifugal extractorsinclude those produced by: Robatel Inc., Pittsfield, Mass.; WestfaliaSeparator Inc., Northvale, N.J.; and Baker Perkins Inc. (Podbielniak),Saginaw, Mich. In the continuous mode of operation, the aqueousproduct-containing feed and the extraction solvent are continuouslycharged to the extractor. The two immiscible phases are intimatelycontacted in the extractor where they flow countercurrently to oneanother. The hydrogen iodide, if present, is converted into iodobutenoland is extracted into the extracting solvent along with the iodide salt.The butenediol products remain in the aqueous phase as it passes throughthe extractor.

The batch, semi-continuous, or continuous extraction may be performedover a wide range of temperatures and pressures. However, the extractiontemperature should remain above the point where a solid phase isgenerated by precipitation or crystallization. As a result, we prefer tooperate the extractor between 10° and 100° C. with a pressure necessaryto prevent evaporation of the solvents.

For dense gas extraction, we prefer to operate the extractor at atemperature between 10° and 150° C., and a pressure between about 1 andabout 450 bar.

EXAMPLES

The present invention is further illustrated by the following examples.The structures of the products obtained were confirmed by nuclearmagnetic resonance spectroscopy and mass spectrometry. All percentagesreported below are based on weight unless otherwise indicated.

EXAMPLE 1 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 30.4 g (0.093 mole) of MeBu₃ NI, 48.0 g of deionized water,and 6.08 g (0.022 mole) of 47% hydriodic acid. The autoclave was sealedand pressurized to 25 psig with helium. The initial reaction mixture hada pH of about 2. Agitation was begun and the mixture heated to 65° C.EPB was pumped in quickly to bring the pH up to 7.8. Thereafter, EPB waspumped into the mixture automatically as needed to maintain a pH of7.3-7.4. The temperature was controlled at 64°-66° C. A total of 20.5 g(0.292 mole) of EPB was added over a period of 363 minutes. A sample ofthe final mixture was analyzed by GC: 12.03% 1,4-butenediol, 1.59%1,2-butenediol, 43.99% water, and 24.71% MeBu₃ NI. The1,4-butenediol/1,2-butenediol ratio was therefore 7.57:1.

The pH and the weight of EPB added as a function of time is graphicallydepicted in FIG. 2. As seen in FIG. 2, the pH remained substantiallyconstant during the reaction as the amount of EPB added to the reactionmixture steadily increased.

EXAMPLE 2 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 15.4 g (0.093 mole) of potassium iodide, 48.0 g of deionizedwater, and 6.08 g (0.022 mole) of 47% hydriodic acid. The autoclave wassealed and pressurized to 25 psig with helium. The initial reactionmixture had a pH of about 2. Agitation was begun and the mixture heatedto 65° C. EPB was pumped in quickly to bring the pH up to 7.25.Thereafter, EPB was pumped into the mixture automatically as needed tomaintain a pH of 7.25. The temperature was controlled at 64°-66° C. Atotal of 14.6 g (0.208 mole) of EPB was added over a period of 339minutes. A sample of the final mixture was analyzed by GC: 11.27%1,4-butenediol, 2.64% 1,2-butenediol, and 60.85% water. The1,4-butenediol/1,2-butenediol ratio was therefore 4.27:1.

EXAMPLE 3 Hydrolysis of EPB

A five-liter, three-neck, round-bottom flask was equipped with amechanical stirrer, pH electrode, condenser, heating mantle, and EPBaddition tubing. The pH electrode was connected to a pH controller whichcontrolled the EPB addition pump. To the flask was charged 669.3 g(2.045 moles) of MeBu₃ NI, 1710 g (95 moles) of water, 30 g (0.11 moles)of 47% aqueous hydrogen iodide, and 138 g (1.53 moles) of1,4-butanediol. The mixture had a pH of 1.05. EPB (14.0 g) was addedslowly to this mixture at room temperature until the pH was 7.0. Theorange mixture was then heated to 65° C. while controlling the pH at 7.4to 7.5 by the automatic addition of EPB. After the solution reached 65°C., the color changed to light yellow and remained that color throughoutthe rest of the EPB addition. The EPB addition rate was about 31 g/min.After 11.5 hours, the heating was turned off and the reactiontemperature allowed to fall (pH control was continued in order tomaintain the pH at 7.4 to 7.5). A total of 376.4 g (5.370 moles) of EPBwas added. The GC assay of the final mixture was 0.20% EPB, 56.2% water,19.1% MeBu₃ NI, 1.5% 3-butene-1,2-diol, 9.3% 2-butene-1,4-diol, and 3.4%1,4-butanediol. The ratio of 1,4-butenediol/1,2-butenediol was therefore6.05:1.

EXAMPLE 4 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 30.4 g (0.093 mole) of MeBu₃ NI, 48.0 g of deionized water,and 6.08 g (0.022 mole) of 47% hydriodic acid. The autoclave was sealedand pressurized to 25 psig with helium. The initial reaction mixture hada pH of about 2. Agitation was begun and the mixture heated to 65° C. Tothe mixture was quickly added (over 7 minutes) 19.3 g (0.28 mole) of EPBgiving a pH of 9.7. Thereafter, the temperature was controlled at64°-66° C. and the pH was allowed to drift. A sample of the mixtureafter 62 minutes (pH 9.5) was analyzed by GC: 0.91% 1,4-butenediol,0.83% 1,2-butenediol, 49.0% water, and 21.9% MeBu₃ NI. The1,4-butenediol/1,2-butenediol ratio was therefore 1.10:1.

After 5.5 hours, the pH had gone to 1.9. A sample of the final mixturewas analyzed by GC: 8.73% 1,4-butenediol, 2.12% 1,2-butenediol, 46.75%water, and 22.2% MeBu₃ NI. The 1,4-diol/1,2-diol ratio was therefore4.12:1.

The pH and the weight of EPB added as a function of time is graphicallydepicted in FIG. 1. As seen in FIG. 1, the pH fluctuated over the courseof the reaction since the EPB was added all at once.

EXAMPLE 5 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 15.4 g (0.0928 mole) of KI, 48.0 g of deionized water, and3.80 g (0.0056 mole) of zinc iodide. The autoclave was sealed andpressurized to 14 psig with helium. The initial reaction mixture had apH of about 6.8. Agitation was begun and the mixture heated to 65° C.EPB was pumped into the mixture automatically as needed to maintain a pHof 7.3-7.4. The temperature was controlled at 64°-66° C. A total of 16.9g (0.241 mole) of EPB was added over a period of 559 minutes. A sampleof the final mixture was analyzed by GC: 14.3% 1,4-butenediol and 2.64%1,2-butenediol. The 1,4-butenediol/1,2-butenediol ratio was therefore5.42:1.

EXAMPLE 6 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 20.2 g (0.0927 mole) of tetramethylphosphonium iodide, 48.0g of deionized water, and 6.08 g (0.0223 mole) of 47% hydriodic acid.The autoclave was sealed and pressurized to 14 psig with helium. Theinitial reaction mixture had a pH of about 1.5. Agitation was begun andthe mixture heated to 65° C. EPB was pumped in quickly to bring the pHup to about 8. Thereafter, EPB was pumped into the mixture automaticallyas needed to maintain a pH of 7.3-7.4. The temperature was controlled at64°-66° C. A total of 19.5 g (0.278 mole) of EPB was added over a periodof 376 minutes. A sample of the final mixture was analyzed by GC: 9.89%1,4-butenediol and 2.24% 1,2-butenediol. The1,4-butenediol/1,2-butenediol ratio was therefore 4.42:1.

EXAMPLE 7 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 30.4 g (0.0929 mole) of MeBu₃ NI, 48.1 g of deionized water,and 3.03 g (0.0111 mole) of 47% hydriodic acid. The autoclave was sealedand pressurized to 14 psig with helium. The initial reaction mixture hada pH of about 2.6. Agitation was begun and EPB was pumped in at roomtemperature to quickly bring the pH up to about 8. The mixture washeated to and held at 64°-65° C. while pumping in EPB automatically asneeded to maintain a pH of 7.3-7.4. A total of 15.9 g (0.229 mole) ofEPB was added over a period of 656 minutes. A sample of the finalmixture was analyzed by GC: 50.68% water, 0.13% EPB, 0.49% DHF, 0.29%crotonaldehyde, 28.3% MeBu₃ NI, 11.53% 1,4-butenediol, and 1.35%1,2-butenediol. The 1,4-butenediol/1,2-butenediol ratio was therefore8.54:1.

EXAMPLE 8 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 30.4 g (0.0929 mole) of MeBu₃ NI, 48.0 g of deionized water,and 6.08 g (0.0223 mole) of 47% hydriodic acid. The autoclave was sealedand pressurized to 14 psig with helium. The initial reaction mixture hada pH of about 1.7. Agitation was begun and the mixture heated to 65° C.EPB was pumped into the mixture automatically as needed to maintain a pHof 2.0. The temperature was controlled at 64°-66° C. A total of 15.3 g(0.218 mole) of EPB was added over a period of 295 minutes. A sample ofthe final mixture was analyzed by GC: 8.89% 1,4-butenediol and 3.88%1,2-butenediol. The 1,4-butenediol/1,2-butenediol ratio was therefore2.29:1.

EXAMPLE 9 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 0.60 g (0.0056 mole) of 2,6-dimethylpyridine, 48.0 g ofdeionized water, and 1.52 g (0.00559 mole) of 47% hydriodic acid. Theautoclave was sealed and pressurized to 14 psig with helium. The initialreaction mixture had a pH of about 3.4. Agitation was begun and themixture heated to 65° C. EPB was pumped into the mixture automaticallyas needed to maintain a pH of 7.4. The temperature was controlled at64°-66° C. A total of 11.4 g (0.163 mole) of EPB was added over a periodof 21.4 hours. A sample of the final mixture was analyzed by GC: 10.3%1,4-butenediol and 0.90% 1,2-butenediol. The1,4-butenediol/1,2-butenediol ratio was therefore 11.4:1.

This example shows that an HI salt of a sterically hindered pyridine canbe used as a source of HI. It also shows the beneficial effect of asterically hindered pyridine as a buffering agent.

EXAMPLE 10 Hydrolysis of EPB

To a 100-mL, stainless steel, stirred autoclave equipped with acondenser, helium supply, back-pressure regulator, EPB feed line (fedfrom a reservoir by a pump), pH probe, heating mantle, and cooling coilswas charged 14.3 g (0.0928 mole) of tetramethylammonium bromide, 48.0 gof deionized water, and 1.9 g (0.011 mole) of 48% hydrobromic acid. Theautoclave was sealed and pressurized to 14 psig with helium. The initialreaction mixture had a pH of about 1.6. Agitation was begun and themixture heated to 65° C. EPB was pumped in quickly to bring the pH up toabout 8. Thereafter EPB was pumped into the mixture automatically asneeded to maintain a pH of 7.3-7.4. The temperature was controlled at64°-66° C. A total of 16.5 g (0.235 mole) of EPB was added over a periodof 363 minutes. A sample of the final mixture was analyzed by GC: 8.95%1,4-butenediol and 6.7% 1,2-butenediol. The1,4-butenediol/1,2-butenediol ratio was therefore 1.34:1.

Comparative Example 1 Hydrolysis of EPB Using Sulfuric Acid Alone

A five-liter, three-neck, round-bottomed flask was set up with a heatingmantle, condenser, thermometer, mechanical stirrer, and addition funnel.To the flask was charged 3000 mL of deionized water and 0.4 mL ofconcentrated sulfuric acid. The pH of the solution was 2. The solutionwas heated to 55° C. then 521.0 g (7.433 mole) of 99.6% EPB was addeddropwise over 90 minutes from the addition funnel. The temperature wasallowed to rise to 77°-85° C. during the addition. The rate of additionwas such that the mixture remained homogeneous. After addition, themixture was refluxed for one hour. GC showed no unreacted EPB, 10%1,4-butenediol, 85.5% 1,2-butenediol, and 4.5% high boilers. The ratioof 1,4-butenediol/1,2-butenediol was therefore 0.12:1.

Comparative Example 2 Hydrolysis of EPB Using Hydriodic Acid Alone

A 500-mL, four-neck, round-bottomed flask was set up with a heatingmantle, condenser, thermocouple, magnetic stirrer, and addition funnel.To the flask was charged 200 mL of deionized water and 4 mL (0.047 mole)of 47% hydriodic acid. The pH of the solution was 1. The solution washeated to 60° C. then 21.6 g (0.308 mole) of EPB was added dropwise over53 minutes from the addition funnel. The temperature was held at 60°-65°C. during the addition. The rate of addition was such that the mixtureremained homogeneous. After addition the mixture was refluxed for onehour. GC showed no unreacted EPB, 1.72% 1,4-butenediol, and 6.99%1,2-butenediol. The ratio of 1,4-butenediol/1,2-butenediol was therefore0.25:1.

EXAMPLE 11 Determination of Distribution Coefficients of Various OniumHalides

Distribution coefficients quantify how solutes, compounds to betransferred across a liquid-liquid interface, will distribute betweentwo immiscible liquid phases at equilibrium. Typically, in liquidextraction a feed that contains one or more solutes is intimatelycontacted with a solvent, and two liquid phases result. The solute(s)transfer from the feed phase into the solvent phase. The feed depletedin the solute(s) is termed the raffinate, and the solvent phase, whichhas gained solute(s), is called the extract. The distributioncoefficients are defined as the concentration of a solute in the extractdivided by the concentration of the solute in the raffinate, and it doesnot need to be greater than unity for the extraction to be feasible.However, larger values of the distribution coefficient are preferred, asthat reduces the solvent requirements and/or the number ofcountercurrent stages required for the extraction. The extractionselectivity refers to the ability of a solvent to extract one compoundin a solution preferentially over another, and it is computed bydividing the distribution coefficient of the solute by the distributioncoefficient of the other component of interest. Thus, the most desirablesolvent would extract a maximum amount of one component and a minimumamount of the other. The extraction selectivity is analogous to therelative volatility for distillation processes. Therefore, its valuemust not equal unity for the separation to be feasible.

The distribution coefficients and extraction selectivities wereexperimentally measured for many onium halide systems includingtetramethyl phosphonium iodide (Me₄ PI), trimethyl phenyl phosphoniumiodide (Me₃ PhPI), dimethyl diphenyl phosphonium iodide (Me₂ Ph₂ PI),methyl triphenyl phosphonium iodide (MePh₃ PI), tetrabutyl phosphoniumiodide (Bu₄ PI), tetramethylammonium iodide (Me₄ NI), tetraethylammoniumiodide (Et₄ NI), tetrabutylammonium iodide (Bu₄ NI), tetrahexylammoniumiodide (Hex₄ NI), methyl tributylammonium iodide (MeBu₃ NI),phenyl-tributylammonium iodide (PhBu₃ NI), tetrabutylphosphonium bromide(Bu₄ PBr), and tetraethylammonium bromide (Et₄ NBr). Approximately twograms of demineralized water, two grams of solvent, and 0.5 grams ofonium halide were added to a graduated glass centrifuge tube. Thesolvent used was EPB, 2,5-dihydrofuran (hereinafter "DHF"), or mixturesthereof. The dispersion was intimately contacted by vortex mixing forfive minutes before it was centrifuged at 2300 times the gravitationalforce for ten minutes. Samples of each phase were taken and analyzed byProton Nuclear Magnetic Resonance Spectroscopy, and the concentration ofwater, solvent, and the onium halide were determined. The distributioncoefficient of the onium halide between the organic- and aqueous-richphases was computed. The extraction selectivity of the solvent for theonium halide with respect to water was then calculated. The results areshown in Table 1.

                                      TABLE 1    __________________________________________________________________________    Phase equilibrium data for the onium halide, water and EPB system as a    function of temperature.                               Organic Phase                   Catalyst                       Organic                           Water                               EPB DHF    Temp.    Organic                   Charged                       Charged                           Charged                               by diff.                                   by diff.                                       Water                                           Cat.    (°C.)        Catalyst             Phase (g) (g) (g) (wt %)                                   (wt %)                                       (wt %)                                           (wt %)    __________________________________________________________________________    25  Me.sub.4 PI             EPB   0.4260                       1.8425                           1.8496                               94.9                                   0.0 5.1 0.0    25  Me.sub.3 PhPI             EPB   0.4089                       1.9024                           2.6700                               94.7                                   0.0 4.9 0.4    25  MePh.sub.3 Pt             EPB   0.4717                       1.8107                           1.8458                               71.6                                   0.0 10.5                                           18.0    25  Bu.sub.4 PI             EPB   0.5310                       1.8720                           1.9182                               71.6                                   0.0 8.1 20.3    25  Et.sub.4 NI             EPB   0.4871                       1.9681                           1.9843                               95.5                                   0.0 4.5 0.1    25  Bu.sub.4 NI             EPB   0.4936                       1.7849                           2.0229                               67.1                                   0.0 11.2                                           21.6    25  Hex.sub.4 NI             EPB   0.4828                       2.1266                           1.8557                               75.4                                   0.0 6.1 18.6    25  MeBu.sub.3 NI             EPB   0.4601                       1.7269                           1.9164                               67.9                                   0.0 13.7                                           18.4    25  Bu.sub.3 PhNI             EPB   0.4021                       1.8933                           1.9682                               77.1                                   0.0 7.5 15.5    25  Bu.sub.4 PBr             EPB   0.4695                       1.7703                           1.9979                               67.9                                   0.0 15.1                                           17.0    25  Et.sub.4 NI             EPB   0.4130                       1.7640                           1.9970                               94.9                                   0.0 5.1 0.0    25  Bu.sub.4 PI             EPB/DHF*                   0.4734                       2.1924                           2.5717                               40.1                                   34.5                                       10.4                                           15.1    25  Bu.sub.4 NI             EPB/DHF*                   0.5197                       2.1972                           2.0026                               34.6                                   31.7                                       15.6                                           18.1    25  Bu.sub.4 PBr             EPB/DHF*                   0.5054                       2.0368                           2.0942                               35.3                                   30.7                                       21.2                                           12.7    25  Et.sub.4 NBr             EPB/DHF*                   0.4831                       1.9026                           1.9320                               49.0                                   43.6                                       7.4 0.0    25  Bu.sub.4 PI             DHF   0.4577                       1.8567                           2.0494                               0.0 68.1                                       14.2                                           17.7    25  Bu.sub.4 NI             DHF   0.4833                       1.8670                           1.9826                               0.0 66.0                                       20.0                                           13.9    25  Et.sub.4 NBr             DHF   0.4726                       2.2443                           2.3148                               0.0 86.0                                       14.0                                           0.0    40  Bu.sub.4 PI             EPB   0.4320                       1.9198                           2.1549                               74.7                                   0.0 8.3 17.0    40  Bu.sub.4 NI             EPB   0.5151                       1.9733                           2.1682                               70.9                                   0.0 10.4                                           18.6    40  Bu.sub.4 PI             EPB/DHF*                   0.4910                       1.9487                           2.3293                               36.6                                   31.6                                       13.7                                           18.1    40  Bu.sub.4 NI             EPB/DHF*                   0.4571                       2.1402                           1.9962                               35.7                                   33.2                                       15.9                                           15.2    40  Bu.sub.4 PI             DHF   0.4635                       2.0480                           2.1791                               0.0 69.1                                       15.2                                           15.8    40  Bu.sub.4 Nt             DHF   0.5146                       2.1551                           1.8511                               0.0 65.8                                       20.7                                           13.5    __________________________________________________________________________                   Aqueous Phase    Distrib.                   EPB  DHF         Coef.                                         Extraction    Temp.    Organic                   by diff.                        by diff.                            Water                                Cat.                                    (org./aq.)                                         Selectivity    (°C.)        Catalyst             Phase (wt %)                        (wt %)                            (wt %)                                (wt %)                                    Catalyst                                         (cat./water)    __________________________________________________________________________    25  Me.sub.4 PI             EPB   6.2  0.0 76.7                                17.1                                    0.0  0.000    25  Me.sub.3 PhPI             EPB   6.6  0.0 81.2                                12.2                                    0.0  0.556    25  MePh.sub.3 Pt             EPB   12.3 0.0 85.0                                2.7 6.5  53.146    25  Bu.sub.4 PI             EPB   10.5 0.0 87.0                                2.5 8.2  88.330    25  Et.sub.4 NI             EPB   19.0 0.0 64.8                                16.2                                    0.0  0.075    25  Bu.sub.4 NI             EPB   10.8 0.0 85.5                                3.7 5.8  43.965    25  Hex.sub.4 NI             EPB   5.0  0.0 94.6                                0.5 40.1 623.812    25  MeBu.sub.3 NI             EPB   11.4 0.0 84.1                                4.5 4.1  25.149    25  Bu.sub.3 PhNI             EPB   5.2  0.0 93.0                                1.7 8.9  110.755    25  Bu.sub.4 PBr             EPB   14.0 0.0 79.8                                6.2 2.8  14.504    25  Et.sub.4 NI             EPB   12.1 0.0 72.4                                15.5                                    0.0  0.005    25  Bu.sub.4 PI             EPB/DHF*                   5.9  13.4                            79.2                                1.5 10.3 78.737    25  Bu.sub.4 NI             EPB/DHF*                   4.0  9.3 84.0                                2.6 6.9  37.123    25  Bu.sub.4 PBr             EPB/DHF*                   4.4  9.6 78.4                                7.5 1.7  6.289    25  Et.sub.4 NBr             EPB/DHF*                   4.0  8.9 69.3                                17.8                                    0.0  0.006    25  Bu.sub.4 PI             DHF   0.0  28.5                            68.4                                3.1 5.7  27.205    25  Bu.sub.4 NI             DHF   0.0  35.0                            59.8                                5.2 2.7  8.002    25  Et.sub.4 NBr             DHF   0.0  20.5                            65.6                                13.9                                    0.0  0.013    40  Bu.sub.4 PI             EPB   15.7 0.0 82.5                                1.8 9.5  94.818    40  Bu.sub.4 NI             EPB   4.6  0.0 91.9                                3.5 5.3  46.965    40  Bu.sub.4 PI             EPB/DHF*                   5.4  11.9                            81.0                                1.7 10.7 63.018    40  Bu.sub.4 NI             EPB/DHF*                   5.6  13.5                            79.0                                1.9 8.0  39.722    40  Bu.sub.4 PI             DHF   0.0  32.9                            64.9                                2.2 7.2  30.924    40  Bu.sub.4 Nt             DHF   0.0  33.3                            61.8                                4.8 2.8  8.343    __________________________________________________________________________     Note: *EPB/DHF mixture was a 50:50 ratio, 20.17 g of EPB and 20.18 g DHF.

EXAMPLE 12 Determination of Distribution Coefficient of MeBu₃ NI

Distribution coefficients typically depend on the solute concentrationin the system. Therefore, the effect of solute concentration on thedistribution coefficient of MeBu₃ NI was more fully investigated at 25°C.

In a first set of experiments, five glass vials were changed with twomilliliters of water and two milliliters of EPB. Then 0.2, 0.4, 0.6,0.8, and 5.0 grams of MeBu₃ NI were added to the first through fifthvials, respectively. The vials were vigorously agitated for five minutesto assure that solute transfer between the phases was complete. Thecontents of the vials were then decanted, and samples of the two liquidphases were taken and analyzed via gas chromatography. The contents ofthe fifth vial were a single liquid phase.

A second set of experiments was then performed to further quantify theeffect of MeBu₃ NI concentration on the distribution coefficient. Thistime ten glass vials were charged with two milliliters of water and twomilliliters of EPB. Then 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0,6.0 grams of MeBu₃ NI were added to the first through tenth vials,respectively. The vials were vigorously agitated for five minutes toassure that solute transfer between the phases was complete. Thecontents of the vials were then decanted, and samples of the two liquidphases were taken and analyzed via gas chromatography. All of the vialsexcept the tenth one formed two immiscible phases. The contents of thetenth vial formed a single liquid phase. Therefore, the soluteconcentration was sufficiently high in that case to homogenize theternary system. The phase volumes in the ninth vial were too small tosample, and the third and seventh samples were contaminated; therefore,the distribution coefficients for these runs are not reported. Thedistribution coefficients for the other experiments are summarized inTable 2.

                                      TABLE 2    __________________________________________________________________________    Phase equilibrium data for the MeBu.sub.3 NI, water, and EPB system at    25° C.                                 Distribution    Tie       Organic Phase                    Aqueous Phase                                 Coefficient                                       Extraction    Line       EPB Water               MeBu.sub.3 NI                    EPB Water                            MeBu.sub.3 NI                                 MeBu.sub.3 NI                                       Selectivity    No.       (wt %)           (wt %)               (wt %)                    (wt %)                        (wt %)                            (wt %)                                 (org./aq.)                                       (cat./water)    __________________________________________________________________________    1  73.22           21.38               5.39 5.47                        91.31                            3.22 1.67  7.15    2  79.48           6.32               14.20                    4.00                        91.96                            4.00 3.55  51.65    3  71.36           7.60               21.04                    4.36                        90.75                            4.88 4.31  51.48    4  64.73           8.87               26.40                    4.73                        90.18                            5.09 5.19  52.73    5  58.82           10.73               30.45                    5.01                        86.99                            8.00 3.81  30.86    6  44.75           14.33               40.92                    5.52                        85.81                            8.67 4.72  28.26    7  31.76           17.41               50.84                    6.54                        77.50                            15.96                                 3.19  14.18    8  26.08           19.61               54.32                    4.26                        82.77                            12.96                                 4.19  17.69    9  23.16           20.78               56.06                    2.91                        82.81                            14.28                                 3.93  15.64    10 20.09           22.32               57.59                    3.57                        79.19                            17.24                                 3.34  11.85    __________________________________________________________________________

EXAMPLE 13 Determination of Distribution Coefficients of 1,2- and1,4-Butenediol

The distribution coefficients for 1,2- and 1,4-butenediol between waterand EPB were measured at 25° C. in this experiment. Two milliliters ofwater and two milliliters of EPB were charged to a series of ten glassvials. Then, the following masses of a 50:50 mixture of 1,2- and1,4-butenediol were added to each vial: 0.25; 0.50; 0.75; 1.00; 1.25;1.50; 1.75; 2.00; 2.25; and 2.75. The vials were vigorously agitated forfive minutes to ensure that solute transfer between the phases wascomplete. The contents of the vials were then decanted, and samples ofthe two liquid phases were taken and analyzed via gas chromatography.The distribution coefficients for these experiments are summarized inTable 3.

                                      TABLE 3    __________________________________________________________________________    Phase equilibrium data for the 1,2- and 1,4-butenediol, water, and EPB    system at 25° C.                               Distribution    Tie       Organic Phase                   Aqueous Phase                               Coefficient                                       Extraction    Line       EPB Water               Diols                   EPB Water                           Diols                               of Diols                                       Selectivity    No.       (wt %)           (wt %)               (wt %)                   (wt %)                       (wt %)                           (wt %)                               (organic/aqueous)                                       (catalyst/water)    __________________________________________________________________________    1  93.64           4.4 1.96                   4.99                       83.68                           11.35                               0.17    3.28    2  93.76           4.35               1.9 6.16                       75.07                           18.77                               0.10    1.75    3  93.1           4.57               2.33                   7.48                       66.14                           26.39                               0.09    1.28    4  91.24           4.89               3.84                   8.89                       58.94                           32.17                               0.12    1.44    5  86.13           7.55               6.32                   11.3                       53.13                           35.56                               0.18    1.25    6  89.17           5.28               5.56                   12.22                       48.74                           39.04                               0.14    1.31    7  92.5           5.97               7.35                   14.36                       43.83                           41.81                               0.18    1.29    __________________________________________________________________________

EXAMPLE 14 Countercurrent Extraction

A six-foot tall, one-half inch diameter, glass, reciprocating-plate,Karr extraction column was operated continuously in countercurrent modefor four hours to separate MeBu₃ NI and iodobutenol catalysts fromaqueous 1,4-diol and 1,2-diol formed by the hydrolysis of EPB. The Karrcolumn consisted of: a five-foot tall active region where Teflon plateswith a one-inch plate spacing and greater than 50% open areareciprocated; two six-inch tall by one-inch diameter expanded coalescingregions at the top and bottom of the extractor to minimize entrainmentof the dispersed phase; and a complete jacket for temperature control.The feed was produced by the hydrolysis reaction of Example 3 andprimarily consisted of EPB, water, MeBu₃ NI, 1,2-butenediol,1,4-butenediol, and 1,4-butanediol at 0.20, 56.2, 19.1, 1.5, 9.3, and3.4 weight percents, respectively. The feed solution was pumped into thetop of the active section of the extraction column at a rate of 14mL/min.; and the solvent, consisting primarily of EPB, entered theextractor at the bottom of the active section at a rate of 14 mL/min.The reciprocation rate was initially 143 strokes per minute (spm) andwas reduced to about 125 spm. The overall column flux was held constantat 325 gph/ft². Samples of the extract and raffinate were periodicallycollected and analyzed, and the results are summarized in the tablebelow. The MeBu₃ NI predominately distributed into the EPB phase whilethe butenediols and 1,4-butanediol preferentially distributed into theaqueous phase. The fraction of catalyst unextracted ranged between 0.055and 0.129 during the course of the run.

    ______________________________________                Elapsed Time                           Fraction of MeBu.sub.3 NI    Sample No.  (minutes)  Unextracted (weight)    ______________________________________    1           0          No Sample    2           19         0.055    3           71         0.069    4           90         0.062    5           102        0.072    6           121        0.073    7           138        0.083    8           187        0.076    ______________________________________

While the invention has been described with reference to the Figures andthe preferred embodiments, it is to be understood that variations andmodifications may be resorted to as will be apparent to those skilled inthe art. Such variations and modifications are to be considered withinthe purview and the scope of the claims appended hereto. For example,the use of hydrobromic acid and/or hydrochloric acid in place of all orpart of the hydriodic acid, and the use of a chloride or bromide salt inplace of all or part of the iodide salt are acceptable variations.

We claim:
 1. A process for separating mixtures of 2-alkene-1,4-diols and3-alkene-1,2-diols from an aqueous mixture comprising (A) an iodidesalt, bromide salt, chloride salt, or mixtures thereof, (B) at least oneof hydriodic acid, iodoalcohol, hydrobromic acid, bromoalcohol,hydrochloric acid, chloroalcohol, and precursors thereof, and (C)2-alkene-1,4-diols and 3-alkene-1,2-diols, said process comprisingcontacting said aqueous mixture with a γ,δ-epoxyalkene-containingorganic extraction solvent at conditions effective to convert saidhydriodic acid, hydrobromic acid, and hydrochloric acid, if present, toiodoalcohol, bromoalcohol, and chloroalcohol, respectively, and to forman aqueous phase comprising said 2-alkene-1,4-diols and3-alkene-1,2-diols, and an organic phase comprising said iodoalcohol,bromoalcohol, or chloroalcohol, and said iodide salt, bromide salt, orchloride salt.
 2. A process for separating mixtures of2-alkene-1,4-diols and 3-alkene-1,2-diols from an aqueous mixturecomprising (A) a bromide salt, (B) at least one of hydrobromic acid,bromoalcohol, and precursors thereof, and (C) 2-alkene-1,4-diols and3-alkene-1,2-diols, said process comprising contacting said aqueousmixture with a γ,δ-epoxyalkene-containing organic extraction solvent atconditions effective to convert said hydrobromic acid, if present, tobromoalcohol and to form an aqueous phase comprising said2-alkene-1,4-diols and 3-alkene-1,2-diols, and an organic phasecomprising said bromoalcohol and bromide salt.
 3. A process forseparating mixtures of 2-alkene-1,4-diols and 3-alkene-1,2-diols from anaqueous mixture comprising (A) an iodide salt, (B) at least one of HI,iodoalcohol, and precursors thereof, and (C) 2-alkene-1,4-diols and3-alkene-1,2-diols, said process comprising contacting said aqueousmixture with a γ,δ-epoxyalkene-containing organic extraction solvent atconditions effective to convert said HI, if present, to iodoalcohol andto form an aqueous phase comprising said 2-alkene-1,4-diols and3-alkene-1,2-diols, and an organic phase comprising said iodoalcohol andiodide salt.
 4. The process according to claim 3, further comprisingseparating said organic phase from said aqueous phase.
 5. The processaccording to claim 3, wherein said γ,δ-epoxyalkene is3-methyl-3,4-epoxy-1-butene, 2-methyl-3,4-epoxy-1-butene,2,3-dimethyl-3,4-epoxy-1-butene, or 3,4-epoxy-1-butene.
 6. The processaccording to claim 3, wherein said γ,δ-epoxyalkene-containing organicextraction solvent comprises a co-extraction solvent selected fromhydrocarbons, haloaromatics, ketones, esters, ethers, amides, andmixtures thereof.
 7. The process according to claim 3, wherein saidγ,δ-epoxyalkene-containing organic extraction solvent comprises a densegas co-extraction solvent selected from carbon dioxide, methane, ethane,propane, butane, isobutane, dimethyl ether, fluorocarbons, and mixturesthereof.
 8. The process according to claim 7, wherein said dense gasco-extraction solvent further comprises a cosolvent selected fromacetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, and mixturesthereof.
 9. The process according to claim 3, wherein said iodide saltis a quaternary ammonium, phosphonium, or arsonium iodide.
 10. Theprocess according to claim 9, wherein said iodide salt is atetraalkylammonium iodide.
 11. The process according to claim 10,wherein said iodide salt is methyltributylammonium iodide.
 12. A processfor separating mixtures of 2-butene-1,4-diol and 3-butene-1,2-diol froman aqueous mixture comprising (A) an iodide salt, (2) at least one ofHI, iodobutenol, and precursors thereof, and (C) 2-butene-1,4-diol and3-butene-1,2-diol, said process comprising contacting said aqueousmixture with a 3,4-epoxy-1-butene-containing organic extraction solventat conditions effective to convert said HI, if present, to iodobutenoland to form an aqueous phase comprising said 2-butene-1,4-diol and3-butene-1,2-diol, and an organic phase comprising said iodobutenol andiodide salt.
 13. The process according to claim 12, further comprisingseparating said organic phase from said aqueous phase.
 14. The processaccording to claim 12, wherein said 3,4-epoxy-1-butene-containingorganic extraction solvent comprises a co-extraction solvent selectedfrom hydrocarbons, haloaromatics, ketones, esters, ethers, amides, andmixtures thereof.
 15. The process according to claim 12, wherein said3,4-epoxy-1-butene-containing organic extraction solvent comprises adense gas co-extraction solvent selected from carbon dioxide, methane,ethane, propane, butane, isobutane, dimethyl ether, fluorocarbons, andmixtures thereof.
 16. The process according to claim 15, wherein saiddense gas co-extraction solvent further comprises a cosolvent selectedfrom acetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, and mixturesthereof.
 17. The process according to claim 12, wherein said iodide saltis a quaternary ammonium, phosphonium, or arsonium iodide.
 18. Theprocess according to claim 17, wherein said iodide salt is atetraalkylammonium iodide.
 19. The process according to claim 18,wherein said iodide salt is methyltributylammonium iodide.
 20. A processfor separating mixtures of 2-alkene-1,4-diols and 3-alkene-1,2-diolsfrom an aqueous mixture comprising (A) an HI salt of a stericallyhindered pyridine and, optionally, an iodide salt, and (B)2-alkene-1,4-diols and 3-alkene-1,2-diols, said process comprisingcontacting said aqueous mixture with an organic extraction solvent atconditions effective to form an aqueous phase comprising said2-alkene-1,4-diols and 3-alkene-1,2-diols, and an organic phasecomprising said HI salt and said iodide salt, if present.
 21. Theprocess according to claim 20, further comprising separating saidorganic phase from said aqueous phase.
 22. The process according toclaim 20, wherein said γ,δ-epoxyalkene is 3-methyl-3,4-epoxy-1-butene,2-methyl-3,4-epoxy-1-butene, 2,3-dimethyl-3,4-epoxy-1-butene, or3,4-epoxy-1-butene.
 23. The process according to claim 20, wherein saidsterically hindered pyridine is 2,6-dimethylpyridine,2,4,6-trimethylpyridine, 2,6-di-tert-butylpyridine,2,6-di-tert-butyl-4-methylpyridine, 2,4,6-tri-tert-butylpyridine,2,6-diphenylpyridine, 2,4,6-triphenylpyridine, acridine, or1,2,3,4,5,6,7,8-octahydroacridine.
 24. The process according to claim20, wherein said organic extraction solvent is selected fromhydrocarbons, haloaromatics, ketones, esters, ethers, amides, andmixtures thereof.
 25. The process according to claim 20, wherein saidorganic extraction solvent is a dense gas selected from carbon dioxide,methane, ethane, propane isobutane, isobutane, dimethyl ether,fluorocarbons, and mixtures thereof.
 26. The process according to claim25, wherein said dense gas further comprises a cosolvent selected fromacetone, tetrahydrofuran, 1,4-dioxane, acetonitrile, and mixturesthereof.